1. Field of the Invention
This invention relates to sound mufflers for vehicles, and particularly, to mufflers of the straight through, glass packed variety.
2. Description of the Known Prior Art
In sound muffling devices used for muffling the sound of operation of an internal combustion engine by passage of exhaust gases from the engine through the muffling device, various types of mufflers have been heretofor proposed and placed in use. In the so called glass pack mufflers, a generally cylindrical shell is used to enclose a layer of glass fiber which surrounds an internal tubular core through which the exhaust gases are passed. The core may be perforated in various ways, and certain types of constrictions or baffle structures can be provided in the core to impart turbulence to the through-flowing exhaust gases, and reduce the noise level of operation of the engine.
It is important in the design construction of mufflers of the type described that any constriction or baffling which is provided not develop excessive back pressure to the exhaust valves of the engine, since this will result in early burning and malfunction of the valves. Moreover, the materials of which the muffler itself is constructed, and particularly the core, must be such, considering the manner in which the exhaust gases flow therethrough, that early burn-outs of the muffler, in which the metal is embrittled and destroyed, do not occur.
Examples of mufflers of the type described, as such have been disclosed in previously issued patents, include those which are illustrated and discussed in U.S. Pat. Nos. 1,638,780 to Neil; 1,861,775 to Aseltine; 2,251,880 to Carey et al.; 2,047,443 to Starkweather et al.; 3,522,863 to Ignoffo and 3,561,562 to Ignoffo.
The prior art thought to be most pertinent with respect to the present invention is that which is illustrated in the two Ignoffo patents referred to above, and in the Aseltine patent. This invention, however, presents certain advantages with respect to the structures in each of these patents, with such advantage residing particularly in the dimensioning and arrangement of certain slots provided in the internal core of the straight-through glass pack muffler, and certain fractional baffling devices in the form of baffle bars which are inserted at certain critical points over the length of the internal tubular core of the muffler.